The prevalence of overweight and obesity has increased dramatically over the last two decades. Overweight and obesity, the second leading preventable cause of death, poses a major public health challenge in that it increases the risk of chronic diseases, including coronary heart disease, and all-cause mortality. Clinic-based programs for weight management are costly and serve only a small percentage of individuals. Population-based behavior change programs are needed to reach larger percentages of at risk individuals more cost-effectively. Preliminary research on the application of the Transtheoretical Model (TTM) to weight management suggests that the model has the potential to guide the development of effective multiple-behavior interventions. Phase I of this Fast-Track proposal involves the customization and feasibility testing of a stage-matched, individualized, interactive intervention based on the TTM. Feasibility includes proactively recruiting 60 percent of eligible participants (n=250) to participate in a randomized clinical trial and evaluating acceptability of the intervention materials. Computerized expert system interventions and stage-matched manuals delivered proactively to entire populations can have unprecedented impacts on the targeted health behaviors as well as weight. Using the TTM as the basis will provide the theoretical framework that experts have indicated is necessary to develop more effective and cost-effective interventions. PROPOSED COMMERCIAL APPLICATION: The proposed TTM based expert system weight management intervention is capable of high recruitment rates, accurate assessment, and individualized interventions that have the ability to create high impact on a population basis. We envision such interactive technologies for entire populations delivered at relatively low costs through the mail or over the Internet or an Intranet. Commercial applications include marketing to healthcare providers, namely managed care organizations, and employers who share the burden of healthcare expenses.